Capacity study of multiuser cooperative networks with fixed-gain relays

In this study, the authors investigate the approximate capacity of a multiuser cooperative networks with fixed-gain relays over independent non-identically distributed Rayleigh fading channels. In order to reduce the complexity, they propose a two-step selection scheme. In this scheme, relay and user selection is processed step by step and relay selection is based on the outdated channel state information (CSI). Finally, the authors show that the closed-form bounds match perfectly with Monte Carlo simulations and although the performance of our scheme is inferior to the optimal joint selection scheme, it is still available in practical scenarios because its low complexity.